A typical metallurgical vessel of the pneumatic type wherein air or oxygen is projected into a molten metal bath generally includes a dished bottom section, a conical upper end and a generally cylindrical central section. Such vessels are commonly supported on a trunnion ring which permits the vessels to be tilted between various operative positions. Trunnion rings are typically water-cooled and are engaged by brackets affixed to the vessel surface. In order to support the vessel in both upright and tilted positions, vessel support systems generally include brackets which engage both the upper and lower surface of the trunnion ring.
Metallurgical vessels of the pneumatic type, such as those employed in basic oxygen processes, are subjected to deformation resulting from conditions encountered during a typical metallurgical operation. Such vessels are generally lined with refractory brick and contain molten metal and slag. The injection of oxygen and fluxes into the vessel produces exothermic reactions resulting in the generation of substantial heat which in turn elevates the temperature of the molten metal and the vessel itself. The inside surface of the refractory brick lining has the highest temperature which is substantially equal to that of the molten metal bath or the effluent gases. A temperature gradient also exists between the inner and outer surfaces of the refractory lining such that the outside temperature of the vessel shell may be several thousand degrees F. lower in temperature than the inside surface of the furnace lining. Nevertheless, the steel shell of the vessel is at a relatively elevated temperature of several hundred degrees F. These relative inner and outer surface temperatures vary during the life of a vessel as a result of changes in refractory thickness caused by wear and surface erosion.
As a result of these thermal stresses, the vessel will grow longitudinally and radially. Trunnion rings, on the other hand, are generally water-cooled and may therefore be several hundred degrees cooler than the surface of the vessel shell. As a result, thermal expansion of the trunnion ring will be relatively insignificant in relation to that of the vessel. Unless means are provided to permit differential expansion of the vessel relative to the trunnion ring, undue stresses will be induced in the vessel surface, the support brackets or in the trunnion ring itself.